High Lockout
D.93 on Vaillant ecoTEC

Your boiler's internal computer has lost its identity settings and doesn't know which specific model it is supposed to be.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

DSN appliance variant setting

What causes this fault?

This fault occurs when the boiler's main control board loses its memory of which specific model it is installed in. The most common reason is that a new control board has been fitted but not yet programmed with the correct identity code, or an electrical surge has corrupted the board's internal settings.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F.70View →F.27View →

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